1. Field of the Invention
The present invention relates to a capillary chip, specifically a capillary chip having a capillary which is useful for conveniently carrying out analyses of a sample in a slight amount.
2. Description of the Related Art
In applications of micromachine techniques, minimization and integration of chemical analysis systems are in one of the most promising fields. Minimized and integrated chemical analysis systems are referred to as micro TAS (Micro Total Analysis Systems). Micro TAS is a system formed on one capillary chip, usually in an about 1 to 2 cm square, comprising a capillary to be a flow channel of a liquid that is a sample and a reagent, a reaction space and a detection space. This system has been expected to attempt saving of the sample, speeding up of the analysis, automatization of the measurement including a pretreatment, rendering the device portable, rendering the device disposable, reducing costs for the device, and the like.
For example, in analytical devices for use in medical diagnoses using blood or the like as a sample, micro TAS is extremely useful which can be conveniently used at the patient's bed side and the like, and which allows the capillary chip that is brought into contact with the sample to be disposable.
Hereafter, development of fine movement control elements such as microvalves which control opening/closing of the flow channel in the capillary chip, liquid delivery driving elements for moving a fluid in a flow channel and the like is indispensable for constructing a sophisticated system in which micro TAS is used.
In general methods of moving a fluid in a flow channel, a liquid delivery pump or a suction pump located outside of the capillary chip is used. In this type of method, due to necessity of an external pump, problems in connection with responsiveness of the control, continuous change, durability, quietness that is important in medical sites and the like are involved. Also, there is the possibility that the device may be entirely enlarged, and that leakage may occur at a junction of the capillary chip with the external pump.
In addition, a method in which a fluid in a flow channel is moved utilizing the electroosmotic flow caused by applying electrophoretic voltage to the liquid in the flow channel has been also known (for example, see JP-A No. H08-261986). According to this method, voltage is applied to the liquid in the flow channel via an electrode, therefore, electrolysis of the measurement sample or the reagent may be caused on the surface of the electrode, leading to alteration of the sample composition or reagent composition.
Further, as the aforementioned microvalve, a valve to occlude the flow channel with wax has been known (for example, see JP-T No. 2000-514928 (the term “JP-T” as used herein means a published Japanese translation of a PCT application)). However, the valve provided using wax involves problems such as limitation of possible application only to flow channels having a great diameter to some extent, adsorption of components in the liquid to the wax, difficulty in controlling rapid opening/closing, and the like.
Moreover, as other microvalve, a valve provided using a coupler has been known (for example, see JP-A No. 2001-165939). Such a valve has a function to arrest the flow of a liquid, which flows into or flows out of a liquid reservoir supplies the liquid to the flow channel, by allowing a coupler to cohere to a part of the liquid reservoir where it opens to atmospheric air and. Movement of the fluid can be recovered by removing the coupler from the cohesive state. However, according to this valve, the coupler must cohere so that airtightness is kept with the liquid reservoir, leading to necessity of complicated production and manipulation. Further, there exists a problem that the opening/closing part of the flow channel can not be optionally selected.
Also, K. Tashiro et al., “A Particles and Biomolecules sorting micro flow system using thermal gelation of methyl cellulose solution”, Micro Total Analysis System 2001, p.471–473 discloses a method in which a flow channel is occluded by preparing a solution which is gelated upon irradiation with a laser, and gelating the solution in the flow channel. However, in this method, a solution which meets a particular requirement must be prepared. Furthermore, although this method can be utilized in occluding a flow channel, use in multiple times as a valve for opening/closing shall be difficult because it goes into a liquid form in its open state.
Additionally, JP-T No. 2003-503716 (the term “JP-T” as used herein means a published Japanese translation of a PCT application) discloses a method of opening/closing a flow channel in which a plug comprising a polymer material is provided in a flow channel, and alteration in the volume of this polymer material is utilized. However, there exist problems in this method that the aforementioned plug must be provided at an arbitrary position, and that opening/closing can not be executed except for the position where the plug is provided.